Today, Maya Yamato and I published a paper, available open-access at PLOS ONE, that gets one step closer to answering those questions. Today's living whales fall into two very ecologically distinct groups: toothed whales, which echolocate; and baleen whales, which filter-feed. These two groups also hear at very different parts of the spectrum, with toothed whales at high frequencies and baleen whales at low frequencies. Since the 1950s, experimental work on captive dolphins has clarified that toothed whales are able to hear the high-frequency sounds (generated from their domed foreheads) using large fat bodies lodged in their jaws, that transmit sound to their ears -- a pathway totally unlike most land mammals, which hear through their ear canal. All whales lack such a canal, but its difficult to trace a hearing pathway in baleen whales for a lot of reasons: their jaws have no such fat bodies that connect to their ear bones, and dissecting them is a rare and unqualified mess.

During her Peter Buck postdoctoral fellowship, Maya turned to a special source of data to approach this problem from another way: could the extensive collections of fetal cetacean specimens at NMNH provide any clues? These collections include rare specimens (many from whaling and commercial fisheries) that are fragile and impossible to dissect by hand in any meaningful way. Instead, Maya did the heavy lifting of CT scanning several dozen specimens (56 in all), across a range of growth stages, and from over 10 different cetacean families, across both toothed whales and baleen whales. Many of these specimens spanned a growth ranges in whale development that have not previously been reported.

We focused our study on a structure known as the "ear trumpet," known to cetacean anatomists for over a hundred years, but difficult to trace through ontogeny unless you know what to look for -- and in the CT datasets, we traced it by way of two ossicles, or small bones of the middle ear: the goniale and malleus (in humans these two bones have complex origins and participate in the middle ear). In all whales the goniale and the malleus begin at a tight V-shaped structure, but soon depart in anatomical orientation depending on where they plot in the whale family tree: the majority have forward-facing ear trumpet, while rorquals and gray whales have side-facing ones. This finding builds on previous work by Maya suggesting that the orientation of the ear trumpet, especially in rorquals, is a solid indicator of the anatomical pathway for hearing in the largest cetaceans ever. Recent modelling studies point to yet more pathways for sound, so the question of how baleen whales (especially rorquals) evolved their unique hearing anatomy, is far from answered! Read our paper for more details!

3D reconstruction of the head of fin whale (Balaenoptera physalus) fetus, based on CT scans of a whole, fluid-preserved specimen (USNM 268884). Incipient ear bones highlighted in yellow, representing the malleus and goniale, become the acoustic funnel. Photo: M. Yamato / Smithsonian Institution.

02/05/2015

All this month, the Smithsonian Field Book Project is celebrating Frederick William True, a scientist, librarian, and administrator who worked for the Smithsonian from 1881 until his death in 1914 (image to the right from SI Archives, MAH-1161716). F. W. True was an important driver for marine mammalogy at the Smithsonian. He helped grow, firsthand, its collections of living and fossil marine mammals, through active fieldwork in Alaska, California, and Maryland. True was also a committed to using this work as a means to engage the public about their natural history, and he helped design and oversee the mounting of large exhibit galleries of cetaceans on the National Mall, both before and after NMNH was built. He authored many landmark contributions about the taxonomy, distribution, ecology and paleobiology of cetaceans. (See his Google Scholar profile here!).

In today's post, BHL's Grace Costantino looks at the origin of F. W. True's landmark study of Delphinidae (oceanic dolphins), and what it means for the history of studying this most species-rich group of cetaceans. Check out Grace's detailed comparison between the number and kinds of species that True noted, and those that are recognized today!

And follow the Smithsonian Transcription Center for the opportunity to participate in the digitization of one of F. W. True's log books from collecting fossil cetaceans in the Calvert Cliffs of Maryland, over 100 years ago. Next month, NDP will be hosting a tour of NMNH's Department of Paleobiology to participants in the project.

02/03/2015

A friend and I were recently trying to decide on what to eat for lunch. He asked, “do you like sushi?” Is that even a question? I love sushi, good sushi. No cuisine provides a better opportunity to sample the great diversity of food from the sea. Of course, there is the fish: salmon, albacore, eel. But there is so much more: seaweed, fish eggs, crab, clam and even sea urchin if you are feeling adventurous.

As a Peter Buck postdoctoral research fellow in the Department of Paleobiology at Smithsonian’s National Museum of Natural History, I study the evolution of animals that have evolved a similar taste for seafood. Just like humans, many different groups of land animal have learned to take advantage of the ocean’s bounty. Some of these land animals have evolved to become dedicated ocean dwellers, giving rise to marine mammals (like whales, sea cows and seals) and marine reptiles (like sea turtles and marine iguanas).

Our modern oceans are not unique in hosting these interlopers. While dinosaurs ruled the land in the Mesozoic (about 250 to 65 million years ago), the oceans were colonized by animals with terrestrial origins: for example fish-shaped reptiles called ichthyosaurs, long-necked plesiosaurs, and gigantic swimming lizards called mosasaurs. I am especially interested how these animals, living and extinct groups descended from land-dwelling ancestors, were able to find a place in ocean food webs. Were they predators or herbivores? Did they eat everything in sight, or were they specialized to eat a narrow variety of foods?

I found that skull and tooth shape very closely match the known diets of living species. Also, species with similar diets–for example sea turtles, sea cows and marine iguanas, which all eat marine plants–show similarities in skull shape despite being descended from very different ancestors. However, within some groups, closely related species have evolved to take advantage of different resources. For example, crabeater seals in Antarctica have specialized teeth for straining krill, while closely related leopard seals have evolved massive skulls and sharp teeth allowing them to feed on a wide range of prey including fish, crustaceans, and penguins.

I am now applying these results to better understand the evolution of diet and feeding styles in extinct marine reptile groups. This work will help to reveal how forces such as climate change and mass extinctions have transformed ocean ecosystems through time, and created evolutionary opportunities for land animals with a taste for seafood.

02/26/2014

Co-author and collaborator Ana M. Valenzuela-Toro reveals MPC 677 (fieldnumber "B33"), with Roberto E. Yury Yáñez (new co-author on another paper), looks on. This image is part of Figure 1 in our new paper published today. (Photo: James F. Parham).

Today, my South American colleagues and I are happy to announce that our paper about our major findings at Cerro Ballena is now available open-access online at Proceedings of the Royal Society B. This work is the result of nearly four years of work aimed at understanding the world’s densest site of fossil whales in Atacama Region, Chile. (See this blog's archive here).

An image from a 3D model of three fossil whales from Cerro Ballena, colloquially called "La Familia." This image is also part of Figure 4 in our paper, out today. See more at http://cerroballena.si.edu

We pull several different lines of evidence to explain how all of these whales, and other marine vertebrates, accumulated at this amazing site: we argue that harmful algal blooms, not just once, but four times (!) were ultimately responsible. The paper is open-access, so go download and read it! And better, yet, see it digitally for yourself at our open-access bilingual (English and Spanish) website designed and built by co-author, information scientist and 3D wrangler, Holly Little:

At the site, anyone can download or interact with 3D models of the fossil baleen whale skeletons; scan GoogleEarth maps of the excavation quarries; look at a vast collection of high-resolution field photos and videos; or move from 360 degree tours of the site. There is also a FAQ (frequently asked questions) page here.

Some of the key members, all co-authors, of our team. See more at http://cerroballena.si.edu (Photo: NDP)

This work was also the result of a great collaboration: 14 co-authors, from students to professors to curators, and across museums and universities internationally. We especially thank our Chilean partner institutions at Museo Nacional de Historia Natural, Chile, the Consejo de Monumentos Nacionales, and Universidad de Chile.

09/24/2013

The view outside my window, for many weeks of the summer. (Photo: NDP)

We are now fully into the fall season here in Washington, D.C., but I wanted to recap briefly on summer goings. Along with a group of researchers from my postdoc days, I spent the summer working at the world's last whaling station in Hvalfjörður, Iceland, for the third time since 2009. Our group continued our series of investigations into the biomechanics and anatomy of lunge-feeding whales (see Publications), including some amazing work by Marina Piscatelli, now a PhD student at UBC. We also got arms deep in pelves, and did some more work on the unusual sensory organ that we reported in Nature in 2012, so keep an eye out on the publications page into 2014.

Meanwhile, 3D digitization of the fossil marine mammal collections continued apace, with 3D digi guru Holly Little spearheading major developments that we will discuss more this coming November. We also hope to share more about our scientific findings on Cerro Ballena this winter -- but not before returning to the Atacama again in just a few days!

12/18/2012

Walking through the airport today, I snagged a copy of the Jan-Feb 2013 issue of Discover magazine. I was elated to see that the rorqual sensory organ was mentioned, sliding in at #74.

(Just ahead of feathered dinosaurs and Jurassic fleas, but well behind the Mars Curiosity rover, which is just fine. That stuff is wild).

For other news stories about the discovery, see links under the Nature paper at the lab's Publications page. We hope to share more about rorqual biomechanics, their evolution and their fossil record in 2013...and if you're going to SICB in San Francisco, be sure to check out Jean Potvin et al.'s posters.

09/17/2012

After a late summer hiatus from our trip in Gondwana, we're back. And we have lots to report. So stay tuned.

While you're waiting, check out the latest from our collaborators (Jean Potvin, Jeremy Goldbogen and Bob Shadwick) about the biomechanics of engulfment feeding in rorquals, published last Friday in PLoS ONE. Read the whole paper here.